linux-kernel - Re: [PATCH] clk: imx8mp: register driver at arch

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Date:   Mon, 21 Nov 2022 17:43:25 +0200
From:   Abel Vesa <abel.vesa@...aro.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Abel Vesa <abelvesa@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH] clk: imx8mp: register driver at arch_initcall time

On 22-09-28 14:41:08, Rasmus Villemoes wrote:
> We have an imx8mp-based board with an external gpio-triggered
> watchdog. Currently, we don't get to handle that in time before it
> resets the board.
> 
> The probe of the watchdog device gets deferred because the SOC's GPIO
> controller is not yet ready, and the probe of that in turn gets deferred
> because its clock provider (namely, this driver) is not yet
> ready. Altogether, the watchdog does not get handled until the late
> initcall deferred_probe_initcall has made sure all leftover devices
> have been probed, and that's way too late.
> 
> Aside from being necessary for our board, this also reduces total boot
> time because fewer device probes get deferred.
> 

I'm gonna be honest here. I can't say I'm happy with this.
I would suggest finding a solution to disable the external watchdog
before booting the kernel, up until the driver probes, would be preferable
to me.

> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
> It would probably be reasonable to do the same to the other imx8m* clk
> drivers, but I don't have any such hardware to test on.
> 
>  drivers/clk/imx/clk-imx8mp.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/imx/clk-imx8mp.c b/drivers/clk/imx/clk-imx8mp.c
> index e89db568f5a8..9ddd39a664cc 100644
> --- a/drivers/clk/imx/clk-imx8mp.c
> +++ b/drivers/clk/imx/clk-imx8mp.c
> @@ -734,7 +734,19 @@ static struct platform_driver imx8mp_clk_driver = {
>  		.of_match_table = imx8mp_clk_of_match,
>  	},
>  };
> -module_platform_driver(imx8mp_clk_driver);
> +
> +static int __init imx8mp_clk_init(void)
> +{
> +	return platform_driver_register(&imx8mp_clk_driver);
> +}
> +arch_initcall(imx8mp_clk_init);
> +
> +static void __exit imx8mp_clk_exit(void)
> +{
> +	platform_driver_unregister(&imx8mp_clk_driver);
> +}
> +module_exit(imx8mp_clk_exit);
> +
>  module_param(mcore_booted, bool, S_IRUGO);
>  MODULE_PARM_DESC(mcore_booted, "See Cortex-M core is booted or not");
>  
> -- 
> 2.37.2
>